Karl Marx's Capital can be read as a work of economics, sociology and
history. He addresses a myriad of topics, but is most generally trying to
present a systematic account of the nature, development, and future of the
capitalist system. There is a strong economic focus to this work, and Marx
addresses the nature of commodities, wages and the worker-capitalist
relationship, among other things. Much of this work tries to show the ways in
which workers are exploited by the capitalist mode of production. He also
provides a history of past exploitations. Marx argues that the capitalist system
is ultimately unstable, because it cannot endlessly sustain profits. Thus, it
provides a more technical background to some of his more generally accessible
works, like The Communist Manifesto.

This study guide focuses on one component of Capital, Marx's schema of
how the capitalist system functions. Marx argues that commodities have both a
use-value and an exchange-value, and that their exchange-value is rooted in
how much labor-power went into them. While traditionally people bought
commodities in order to use them, capitalists use commodities differently. Their
final goal is increased profit. Therefore, they put out money and buy
commodities, in order to sell those commodities for a profit. The cycle then
repeats itself. The reason why the capitalists are able to make a profit is that
they only need to pay workers their value (how much it takes to keep them
functional), but the workers produce more than that amount in a day. Thus, the
workers are exploited. The capitalists are able to do this because they have
more power, and control the means of production. Furthermore, the workers'
character is negatively affected by the system. They don't own the products of
their labor, and the repetitive work they have to do makes them little more than
machines.